Ciancia, who police say shot and killed a Transportation Security Administration screener at LAX, was dropped off at the airport by one of his roommates about 9 a.m. Friday, shortly before the deadly shooting rampage occurred, according to authorities.

Around the same time, Los Angeles police officers paid a visit to his apartment in Sun Valley in response to concerns from his family after they received text messages indicating that he wanted to harm himself.

"This is how we typically stop these things -- through good intelligence, and if family members or friends see a loved one who is exhibiting signs of mental illness ... then I think it's incumbent to call this to local authorities," McCaul said. "They actually did that in this case and, unfortunately, missed the suspect by a matter of minutes."

Officers were following up in response to an alert from Ciancia's family that the 23-year-old had sent text messages to his brother and sister Friday indicating that he wanted to harm himself, Allen J. Cummings, police chief of Ciancia's hometown of Pennsville Township, N.J., told The Times.

Later that day, with news crews swarming LAX, Ciancia's father called Cummings. "I'm watching TV," he told the chief, "and I think this is my son at the airport."

There had been no indication the 23-year-old was struggling, or that he may have harbored anti-government sentiments, Cummings said.

"We don't really know what happened out West," he said. "We don't know where he got his ideas or where that came from."

Ciancia, who moved to Los Angeles about 18 months ago, was carrying a signed, handwritten note in his duffel bag referring to TSA officials that said he wanted to "instill fear into their traitorous minds," according to the FBI.

"His intent was very clear in his note," said David Bowdich, special agent in charge of the Counterterrorism Division at the FBI's Los Angeles office. "In that note he indicated his anger and his malice toward the TSA officers."

A law enforcement official told The Times that the screed resembled a "suicide note." The gunman said he didn't want to hurt anyone "innocent" — only TSA agents. The note also mentioned "NWO," a possible reference to the New World Order, a conspiracy theory that holds that forces are trying to create a totalitarian one-world government.

When he entered LAX, Ciancia was wearing dark clothes and a bulletproof vest and had not purchased a ticket. He carried a Smith & Wesson .223-caliber M&P-15 assault rifle, five loaded magazines and a trove of ammunition, Bowdich said.